Connect By Query Level is becaming 0

Question

Hi
I am using a sub query as below and I started to get ORA-01428 errors randomly in one schema.
Then while debugging I found out that level is getting value 0 in that schema and this is freaking out INSTR.
Both databases are on the same patch level and this is happening randomly.
Why does the value of level become 0? How can I avoid it ?
I realized that CBO is taking a different path to execute the query when it doesn't work..
Thanks a lot.
--sfnc is a logging function that I added to see the value of level, I don't have this in the actual query. It returns back what it gets.
With selected_dates As (
                      Select to_date(SUBSTR(:p_dates,
                      INSTR('|' || :p_dates, '|', 1, sfnc(level)),
                      INSTR(:p_dates || '|', '|', 1, sfnc(level)) - INSTR('|' || :p_dates, '|', 1, sfnc(level))),'DD/MM/YYYY') dt
                        From dual
                     Connect By Level <= LENGTH(:p_dates) - LENGTH(Replace(:p_dates, '|')) + 1
                        ANd  Prior dbms_random.Value Is Not Null
-Edited by: Muhammed Soyer on Aug 28, 2009 10:31 AM

Answer 1

Hi,
You may be a victim of "Bug 6679575 Wrong results from CONNECT BY and WITH clause" (see Metalink):
Versions confirmed as being affected     
* 10.2.0.3
* 10.2.0.4
Wrong results can be returned for an inlined WITH clause within
a view using a CONNECT BY "LEVEL" pseudo column.
Workaround:
Ensure that the WITH clause is materialized.
eg: MATERIALIZE hint
Note:
Also see bug 6643093 as materialized WITH clauses can also
give wrong results without that fix.
or "Bug 6643093 Wrong results from CONNECT BY and WITH clause":
>>
Versions confirmed as being affected     
* 10.2.0.3
Wrong results may be returned for materialized WITH clauses .
The plan output shows predicates of the form
NULL IS NOT NULL
Workaround
Use a stored view instead of a WITH clause.Hope this helps,
Vincent
Edited by: user10285933 on 28 août 2009 13:47